我正在嘗試從Cloud Firestore數(shù)據(jù)庫(kù)中檢索一組復(fù)雜的對(duì)象。這是我的課：public class Book {    private String id;    private String name;    private String original;    private ArrayList<Author> authors;    private ArrayList<Translator> translators;    private Series series;    private Float no;    private String seriesNo;    private Integer published;    private Borrower borrower;    private Boolean isCollection;    private Status status;}將此Book對(duì)象保存到數(shù)據(jù)庫(kù)的最佳方法是什么？我目前正在使用以下方法。public void createBook(String userId) {    FirebaseFirestore firebaseFirestore = FirebaseFirestore.getInstance();    DocumentReference documentReference = firebaseFirestore.collection("books").document();    Map<String, Object> newBook = new HashMap<>();    newBook.put("owner", userId);    newBook.put("id", documentReference.getId());    newBook.put("name", getName());    newBook.put("original", getOriginal());    if (getSeries() != null) {        Map<String, Object> series = new HashMap<>();        series.put("id", getSeries().getId());        series.put("name", getSeries().getName());        newBook.put("series", series);    }    newBook.put("no", getNo());    newBook.put("seriesNo", getSeriesNo());    newBook.put("published", getPublished());    if (getBorrower() != null) {        Map<String, Object> borrower = new HashMap<>();        borrower.put("id", getBorrower().getId());        borrower.put("nameInEnglish", getBorrower().getNameInEnglish());        borrower.put("nameInSinhalese", getBorrower().getNameInSinhalese());        borrower.put("mobile", getBorrower().getMobile());        newBook.put("borrower", borrower);    }    newBook.put("isCollection", getIsCollection());    newBook.put("status", getStatus().toString());從數(shù)據(jù)庫(kù)中檢索保存的值的最佳方法是什么？很難找到一種同時(shí)訪問(wèn)所有值的好方法。我目前使用以下方法來(lái)檢索除 Authors 和 Translators（它們是 ArrayLists）之外的值。